Differences between measured and simulated results of antenna efficiency

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YechielA

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Hi,

I simulates a simple printed Inverted -F antenna at a frequency of 1.9 GHz using HFSS. I also measured the antenna in an anechic chamber.
The problem is that I get a large difference between simulated and measured results. While measured results show antenna efficiency of about 66%, measured results show no more then 27%. The printed antenna is printed on FR4 which is assumed to have a TAND of 0.02.
 

Hi,

I also have similar observations. I measured several printed antennas in an anechoic chamber. In some cases, the results were close but in other cases, there was a huge difference. HFSS gave a 94% efficiency of a printed monopole designed on FR4 substrate. However, when measured in Satimo anechoic chamber, the actual efficiency was only 56%. For the patch antenna, the measured readings were mostly the same.
If you get to know how to get accurate efficiency with HFSS, please share.
Also there is a Wheeler's cap method to test the antenna efficiency using network analyzer. I never get the correct reading using that method. If anyone knows about this method, please share.
 

"Wheeler's cap method" - didn't hear about it. I'll learn about it. There is a small test equipment also provided by EMSCAN called RFX/RFX2 for efficiency and radiation pattern. it does a near field to far field transformation.
 

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